1. Field of the Invention
The present invention relates to the field of integrated circuits. More particularly, the invention provides a heat sink for use with stacks of integrated circuits.
2. Description of the Related Art
As computer manufacturers have attempted to build more powerful machines, the use of chip stacks in modem computing applications has become increasingly desirable. The term `chips` used with the present invention is intended to include any packaged integrated circuit device including processing devices e.g. microprocessors etc., memory devices e.g. DRAMS, SRAMS, etc., and the like. In essence, a chip stack comprises multiple integrated circuit packages which are stacked together (back-to-front or back-to-back). The chip stacks may be oriented either in face up position or in a side-to-side orientation with chip edges down.
There are a number of advantages to the chip stack configuration over conventional single chip mounting arrangements. In particular, the chip stacks provide a more compact circuit arrangement for computers and other high speed electronic systems.
In addition, chip stacks particularly allow for more efficient use of space on circuit boards. The stack takes advantage of relatively less valuable space above the circuit board, while at the same time leaving a small footprint on a circuit board or card, thereby increasing the space available for other components or chip stacks.
While there are numerous advantages to a stacked chip configuration, there are also associated problems. Specifically, larger and larger chip stacks create unique cooling problems. Because the chip stacks contain multiple chips, they generate more heat per unit volume, requiring greater heat dissipation, while at the same time providing significantly smaller surface areas which may be used as a heat sink. In view of this problem, the general response in the industry to the need for cooling chip-stacks has been to immerse the entire chip-stack in liquid or to operate at greatly reduced power levels. This is often an unwelcome solution because of technical concerns and also because of customer and user preferences.